1. Field of the invention
The invention relates to apparatus for treating a granular substance, especially nuclear reactor fuel in powder form, with a treatment drum which is supported rotatably about a central axis and can be driven about this central axis by means of an associated drive unit and has a cover at one end, and a method for operating the apparatus.
2. Description of the Prior Art
Such apparatus, designed as a ball mill, is commercially available. The treatment drum which can be filled with milling balls, is closed at one end by a one-piece cover which is pressed from the outside by means of a screw into the charging opening of the treatment drum which is located at this end. The screw is guided in a tapped hole which is made in a cross piece arranged crosswise over the opening with a cover and is held at both ends by a ring which is clamped on the outside to the cylinder surface of the treatment drum. The treatment drum is loosely supported with its outer cylinder surface and with the central axis horizontal between two cylindrical rolls on the cylinder surfaces of these two rolls which are arranged side by side with horizontal and mutually parallel longitudinal axes. One of these rolls is driven about its longitudinal axis by means of an electric motor and thus represents the drive unit which is associated with the treatment drum and by which the treatment drum can be driven about its central axis and is rotated.
The granular substance to be treated can be poured by hand into the treatment drum which is arranged with the central axis vertical, and can be poured out of the treatment drum after the treatment therein. This results of necessity in considerable dust development which can endanger the operating personnel especially in the case of a toxic or radioactive (for instance plutonium-containing) granular substance.